Race Primary Belt to Chain Conversion Kit | 420 RK MXZ | Surron Ultra BeeUltra Bee Primary Chain Drive Racing Kit With 420 RK MXZ Sealed Chain For serious off road and moto racers the non sealed RK MXZ chain kit is the most efficient kit with the least amount of parasitic drag More Efficient Than Belt Better Acceleration Longer Run Time Easy Maintenance Similar To Stock Gear Ratio Chain can be replaced without removing the swing arm There is a good reason that we do not offer a 520 size chain for this bike. Over the same